[time-nuts] Ebay FE-5680A Rb: Are they that good?
lists at rtty.us
Sat Dec 10 10:37:07 EST 2011
If you dig into the circuit, the resolution of the DDS is indeed 7x10^-13 per LSB.
On Dec 9, 2011, at 9:51 PM, Bob Smither wrote:
> Bob Smither wrote:
>> My documentation states that the full range of adjustment is:
>> 7f ff ff ff => +383 Hz
>> 80 00 00 00 => -383 Hz
> This scale factor is clearly wrong - using it and applying an appropriate correction changes the frequency way too much.
> (thanks Jose!) a better estimate is 140000 / Hz.
> Using data after 20 hours:
> the estimated frequency offset is 1.36E-3 Hz. Using the above scale factor gives a correction of -190 counts. Here is the command I used to (temporarily) program the new offset:
> 2e 09 00 27 ff ff ff 42 bd
> (the bd is the exclusive-or checksum of the offset)
> Now I wait ...
> Bob Smither, PhD Circuit Concepts, Inc.
> A government which robs Peter to pay Paul can always depend on the
> support of Paul.
> --George Bernard Shaw
> Smither at C-C-I.Com http://www.C-C-I.Com 281-331-2744(office) -4616(fax)
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